Simon Bellamy was a 18 year old boy who is put on community service for trying to burn a bully's house down whilst drunk. He is the shy nerd who doesn't connect with the other members of the group. Kelly stands up for him against Nathan, who bullies him. Curtis and Alisha look down at him. Others never notice or see his power (Invisibility) and often seem to doubt it's real. Curtis believes in Simon's ability, as Simon indicated he had seen a personal moment between him and Alisha in Episode Three. In a scene published on the Misfits website in week five, Simon films Kelly while invisible and then reappears in front of her, proving to her that his power is real. When Simon turns invisible, his head and hands move at superspeed, and his mouth and eyes widen in pain. In the third episode, it is suggested that Simon is losing control of his power, as he collapses to the ground moaning when he turns invisible, apparently against his will. However, by the fifth episode Simon demonstrates far greater proficiency with his ability, turning invisible at will and quickly, as well as affecting objects around him.

Simon is portrayed as the smartest individual of the group as seen in episode three, where he devises a plan to permanently 'hide' the corpses of the Misfits' dead probation worker and their former colleage Gary. He has no real friends; the Misfits refuse to go for a drink with him, and he is mistakenly invited to a party by someone thinking he was a different Simon in Episode Four. He is constantly attached to his camera phone, using it to film the storm and occasionally his fellow ASBO holders. In Episode Two, he is contacted online by "Shygirl18", who expresses an interest in his videos of the storm. We discover that "Shygirl18" is in fact the dead probation worker Tony's partner, Sally, who suspects that the Misfits were involved in Tony's disappearance and tries to get close to Simon in an attempt to find out more. Although she apparently expressed an interest in him, Simon later learns that she was simply using him to find out what had happened to Tony, accidentally killing her in the subsequent fight when she threatened to tell the police he and the Misfits had done. Simon hides her body in an industrial freezer in the community centre, which he visits often. He does not tell the others about her death, as revealed in episode six.

When Rachel Leyton and the Virtue Organization take control of Wertham, he and Nathan are the only survivors. On the roof of the Community Centre, Simon was Invisible, hiding from the Virtues. He sees Rachel trip and fall off and Nathan falling back as well. Simon jumps out and tries to save Nathan, despite his bullying. Nathan falls anyway, and is impaled on the spikes below.